John D. Fitzsimons

Development of Thiamine Deficiencies and Early Mortality Syndrome in Lake Trout by Feeding Experimental and Feral Fish Diets Containing Thiaminase

Abstract We conducted a laboratory investigation on the consequences of feeding predatory salmonids either experimental diets low in thiamine or diets containing alewife Alosa pseudoharengus. In experiment 1, adult lake trout Salvelinus namaycush were fed experimental diets containing bacterial thiaminase. In experiment 2, adult lake trout were fed natural prey species, alewives, and bloaters Coregonus hoyi. The diets consisted of four combinations of alewives and bloaters from Lake Michigan (100% alewives, 65% alewives–35% bloaters, 35% alewives–65% bloaters, and 100% bloaters), alewives from Cayuga Lake, a casein bacterial thiaminase, and a commercial trout diet. We assessed the effects of each diet on egg thiamine concentration and incidence of an embryonic early mortality syndrome (EMS). In experiment 1, incidence of EMS ranged from 0% to 100%. Significant relationships were found between the incidence of EMS and thiamine. In experiment 2, adult lake trout fed 100% alewives from either Lake Michigan o...

Thiamine and Thiaminase Status in Forage Fish of Salmonines from Lake Michigan

Abstract Dietary sources of thiamine (vitamin B1) and thiamine-degrading enzymes (thiaminases) are thought to be primary factors in the development of thiamine deficiency among Great Lakes salmonines. We surveyed major forage fish species in Lake Michigan for their content of thiamine, thiamine vitamers, and thiaminase activity. Concentrations of total thiamine were similar (P ≤ 0.05) among most forage fishes (alewife Alosa pseudoharengus, bloater Coregonus hoyi, spottail shiner Notropis hudsonius, deepwater sculpin Myoxocephalus thompsonii, yellow perch Perca flavescens, ninespine stickleback Pungitius pungitius, and round goby Neogobius melanostomus) and slightly lower in rainbow smelt Osmerus mordax. Concentrations of total thiamine were all above the dietary requirements of coldwater fishes, suggesting the thiamine content of forage fish is not the critical factor in the development of thiamine deficiency in Lake Michigan salmonines. Thiamine pyrophosphate was the predominant form of thiamine in most ...

The Effect of B-Vitamins on a Swim-up Syndrome in Lake Ontario Lake Trout

Abstract Collect ions of lake trout spawners and eggs were made in Lake Ontario to assess the ameliorative effects of several B-vitamins (thiamine, riboflavin, folic acid, nicotinic acid, pyridoxine hydrochloride) on mortality associated with swim-up syndrome. Vitamins were administered either by water immersion (1 gm/L to eggs from one female) or intraperitoneal injection (30 ppm to eggs from five females) into the yolk sac. Thiamine, but none of the other B-vitamins, was effective both in reversal and prevention of the clinical signs and mortality associated with the syndrome.

Implications of Thiamine Deficiency in Great Lakes Salmonines

Abstract Our recent experimental work and ecoepizootiological assessments provide mechanistic data supporting a plausible hypothesis for an association between a prey base comprised of a large biomass of nonnative alewives Alosa pseudoharengus and the recruitment difficulties currently experienced by Great Lakes salmonines. We hypothesize that the thiamine deficiency induced by alewives, a species harboring high thiaminase activity, represents an ongoing cause of fry and adult mortality in salmonines. Overall ramifications of the thiamine deficiency on recruitment have not been firmly established but may represent a substantial bottleneck for natural recruitment in feral salmonine populations in the Great Lakes.

Assessment of Lake Trout Spawning Habitat and Egg Deposition and Survival in Lake Ontario

Identification of the amount of lake trout spawning habitat and its actual use by lake trout in Lake Ontario is important for re-establishment of this species. From a combination of hydrographic field data, bathymetry measurements, and video observations, 20 reputed spawning sites, 14 of which were considered to be historically important, were evaluated for possible use by lake trout. Based on preliminary evaluations 13 of the 20 sites were rejected for further study because of inappropriate substrate or excessive infilling of interstitial spaces. Additional, more intense evaluations were made of seven sites, five that were of historical importance and two that were man-made. These seven sites had areas of suitable spawning habitat of from 6 to 4,000 m2, minimal water depths of from 2.2 to 10.8 m, mean cobble diameters of 9.8–20.0 cm, and slopes of 20–45°. Lake trout egg densities, estimated from recoveries in egg nets deployed in 1992, ranged from a mean of 6 to 6,200 eggs m−2 and the highest densities were found at man-made sites. The actual egg deposition on the seven sites studied intensely amounted to only 0.0003 to 0.6% of the potential deposition if all the lake trout that survived from stocking within a 30 km radius of each site spawned there. Egg survival to the eyed stage ranged from 21 to 82% and was inversely related to wind fetch. Spawning was earlier in western than in eastern Lake Ontario and was related to the rates of fall cooling. Duration of the spawning period ranged from 1 to 39 days but the low estimates were from collections of only a few eggs. A swim-up mortality syndrome observed in eggs reared in a laboratory was high, ranging from 31.0 to 74.5%. The potential for lake trout restoration in Lake Ontario appears to be limited by a scarcity of good spawning sites, low egg deposition on spawning sites recognized by researchers, and excessive swim-up mortality.

Lake Trout Spawning Habitat in the Great Lakes — a Review of Current Knowledge

Abstract We review existing information on lake trout spawning habitat, which might indicate whether habitat is now a limiting factor in lake trout reproductive success. Lake trout spawning habitat quality is defined by the presence or absence of olfactory cues for homing, reef location with respect to the shoreline, water depth, proximity to nursery areas, reef size, contour, substrate size and shape, depth of interstitial spaces, water temperature at spawning time, water quality in interstitial spaces, and the presence of egg and fry predators. Data on factors which attracted native spawners to spawning reefs are lacking, due to the absence of historic data on egg deposition. No direct evidence of egg deposition has been collected from sites deeper than 18 m. Interstitial space and, therefore, substrate size and shape, appear to be critical for both site selection by adults and protection of eggs and fry. Water quality is clearly important for egg incubation, but the critical parameters which define water quality have not yet been well determined in the field. Exposure to wave energy, dictated in part by reef location, may maintain high water quality but may also damage or dislodge eggs. The importance of olfactory cues, water temperature, and proximity to nursery habitat to spawning trout is unclear. Limited data suggest that egg and fry predators, particularly exotic species, may critically affect fry production and survival. Although availability of physical spawning habitat is probably not limiting lake trout reproduction, changes in water quality and species composition may negatively affect early life stages. This review of habitat factors that affect early life stages of lake trout suggests several priorities for research and management.

Occurrence of a Swim-up Syndrome in Lake Ontario Lake Trout in Relation to Contaminants and Cultural Practices

Collections of lake trout eggs were made from Lake Ontario adults to evaluate the occurrence of a swim-up mortality syndrome and determine its relationship to cultural practices and egg contaminant burdens (PCBs, pesticides, dioxins, furans, polynuclear aromatic hydrocarbons, and trace metals). The syndrome, characterized by hyperexcitability, anorexia, loss of equilibrium, and eventual death, was observed in fry hatched from eggs of 21 of 24 (87.5%) females. Mortality due to the syndrome averaged 33.5% but was not correlated with fertilization rate, hatching rate, or any of six specific mortality types monitored in eggs and fry. Occurrence of the syndrome was not related to rearing temperature (i.e., 4°C vs. 8°C) or feeding (i.e., fed vs. unfed). No significant correlations existed between any of the contaminants measured and either swim-up syndrome mortality or the six mortality types monitored.

Laboratory Estimates of Salmonine Egg Predation by Round Gobies (Neogobius melanostomus), Sculpins (Cottus cognatus and C. bairdi), and Crayfish (Orconectes propinquus)

ABSTRACT The continued lack of natural reproduction by lake trout (Salvelinus namaycush) in the Great Lakes has prompted development of models focused on the potential negative effects of interstitial predators. To aid in parameterization of such models we investigated the effect of temperature (1–2°C, 4–5°C, 7–8°C, and 10–11°C), predator group size, interspecific competition, egg density (60–6000 eggs m−2), and an alternate food source on egg consumption by slimy (Cottus cognatus) and mottled (Cottus bairdii) sculpins, round gobies (Neogobius melanostomus), and the native crayfish (Orconectes propinquus) in the laboratory. Egg consumption by the sculpins and round goby all increased over the range of temperatures investigated (ca 0.5 eggs·day−1 at 1–2°C to 1.5 eggs·day−1 at 10–11°C). Predator group size affected consumption; fewer eggs were eaten per individual slimy sculpin and round goby at densities of 5 or 10 per tank than 1 individual per tank. There was no effect of interspecific competition on egg consumption by slimy sculpins or round gobies at a density of 10 individuals per tank for various species combinations (10:0, 9:1, 5:5, 1:9, 0:10). A type II functional response to egg density was observed for sculpins, gobies, and crayfish although at extreme densities per capita consumption by crayfish and gobies declined. The presence of zebra mussels (Dreissena polymorpha) did not affect the number of rainbow trout (Oncorhynchus mykiss) eggs eaten by round gobies whose mussel consumption averaged 75% BW·day−1. Of the four species examined, round gobies appeared to be the most effective egg predator while crayfish were the least.

Thiamine Status in Adult Salmonines in the Great Lakes

Abstract In 1996 and again in 1999, hatchery personnel noted that some Lake Michigan coho salmon Oncorhynchus kisutch from fall spawning runs on the Platte River weir exhibited abnormal wiggling behavior that was similar to the behavior exhibited by thiamine-deficient Atlantic salmon Salmo salar, from the Baltic Sea. Samples of eggs or gonads, muscle, and liver from salmon and lake trout Salvelinus namaycush exhibiting abnormal behaviors were collected to determine the extent to which the behaviors were related to a thiamine deficiency. We compared these values with those found in normally behaving fish that produced offspring with high embryonic survival. In all adult fish exhibiting abnormal behavior, tissue residues of thiamine were among the lowest observed in the Great Lakes. Where embryonic survival was assessed, abnormal adult behavior was also associated with very high levels of offspring mortality due to early mortality syndrome. While the overall ecological significance remains to be determined,...

Influences of Spawning Habitat Characteristics and Interstitial Predators on Lake Trout Egg Deposition and Mortality

Abstract To understand the factors affecting natural recruitment of lake trout Salvelinus namaycush, we evaluated natural egg deposition, the rate of egg loss of seeded eggs, and the relationship of interstitial predators to egg mortality at a protected nearshore lake trout spawning area in Lake Michigan. Egg mortality and predator densities were evaluated with collection bags that were buried above the drop-off on spawning substrate at 1-, 3-, and 9-m depths. Habitat selection by spawning lake trout was probably related to the coverage by periphyton and zebra mussels Dreissena polymorpha given that abiotic characteristics of the spawning habitat such as slope (55– 65°), interstitial depth (30–50 cm), and substrate type did not differ across depths. The results of seeding eggs during spawning and recovering them throughout the incubation period (2–177 d) indicated that egg mortality was extremely high early in the spawning period: Over 40% of seeded eggs were lost by 2 d and over 80% of the eggs were lost...